One conventional method of forming a situ wall surfaces involves spraying or projecting plaster or mortar onto a mesh lath. A typical mesh lath is formed by expanded metal which may be reinforced with integrally rolled ribs.
When a mesh lath has plaster or mortar sprayed or projected onto it, the plaster or mortar envelopes the strands of the mesh and forms a continuous surface at least on the front of the lath. However, as much as 25% or more of the plaster or mortar would pass through the openings in the mesh and be wasted unless some backing is provided on the lath. It is known to provide such a backing in the form of a sheet of paper which is stapled, sewn, or bonded to the lath. The fixing of the sheet of paper to the lath is not an easy operation and the paper is liable to become torn during handling, particulary if it becomes wet.
It has been proposed, in British Specification No. 1,211,700, to apply to a mesh lath either globules of foamed synthetic resin or a flock coating. It is believed that these techniques have never been used commercially and they are quite impracticable. This is because neither the globules of foamed synthetic resin nor the flock fibres will project sufficiently across the apertures of the mesh to impede the plaster or mortar to any useful extent and the flock coating will be unacceptably expensive in requiring both the application of an adhesive and of staple fibre, usually in an electrostatic field. Further, the type of coating described will not expand in order to accept the correct amount of plaster as the plaster or mortar is directed against the coated mesh lath.
U.S. Pat. No. 3,072,497 - Guglielmo Sr., et al, describes the coating of open mesh materials, including metal laths. In particular, that patent is directed to a method of coating such a lath and the net result is a continuous coating of the plastic across both faces of the lath. In particular, this is shown by FIGS. 4 and 5 and their description which shows the solid portion of the lath to be covered, front and back, by the resin coating. Still further, that patent discloses at Column 4, in the paragraph beginning at line 49, that the viscosity of the coating material should be high so as to insure a continuous film. The structure resulting will not function in the same efficient way as the structure of the present invention.